ITTO20120426A1 - PROCESS OF MANUFACTURING A NOZZLE PLATE, NOZZLE PLATE, AND LIQUID EJECTION DEVICE EQUIPPED WITH NOZZLE PLATE - Google Patents

Description

DESCRIPTION

â € œPROCESS OF MANUFACTURING A NOZZLE PLATE, NOZZLE PLATE, AND A LIQUID EJECTION DEVICE WITH THE NOZZLE PLATEâ €

The present invention relates to a process for manufacturing a nozzle plate, a nozzle plate, and a liquid ejection device comprising this nozzle plate.

Liquid ejection devices in the form of drops (such as for example inhalers, printer heads, etc.) generally comprise a nozzle plate arranged facing a reservoir containing the liquid to be ejected. An actuation element, such as a piezoelectric, can be used to deform the tank and cause the liquid to escape through the membrane nozzles. Another known technology of liquid ejection is the thermal technology (known as thermal inkjet or bubble inkjet), in which a heater, placed between each nozzle and the tank, is able to generate a vapor bubble that causes the € ™ ejection of liquid from the respective nozzle.

It is clear that, regardless of the ejection technology used, the size and shape of the nozzles, as well as the uniformity of the size and shape of the nozzles, are particularly important parameters for defining the size and direction of the drops generated and their reproducibility.

Generally, the nozzles have a cylindrical shape with an outlet diameter smaller than the diameter of the channel which feeds the liquid to be ejected to the nozzles. Often, between the supply channel and the respective nozzle, there is also a connection element with a substantially truncated cone shape having a larger base section (with a diameter equal to the diameter of the supply channel) coupled to the supply channel itself. , and a smaller base section (with a diameter equal to the diameter of the nozzle base section) coupled to the nozzle. This configuration allows to increase the ejection speed of the generated drops. However, the coupling phase, in particular between the connecting element and the nozzle, is not easy, and often causes unwanted misalignments.

Furthermore, nozzles having an outlet mouth protruding from the nozzle plate are particularly subject to damage, and to the unwanted deposit of material capable of creating an obstacle to the ejection of the liquid. A further disadvantage of such nozzle plates is the dependence of the ejected drop on the external structural conformation of the nozzles.

The purpose of the present invention is to provide a manufacturing process for a nozzle plate for a liquid ejection device, a nozzle plate for a liquid ejection device, and a liquid ejection device using such a nozzle plate, free from the drawbacks of the known art.

According to the present invention, a manufacturing process of a nozzle plate for a liquid ejection device, a nozzle plate for a liquid ejection device, and a liquid ejection device using such a nozzle plate, such as defined in the attached claims.

For a better understanding of the present invention, preferred embodiments are now described, purely by way of non-limiting example, with reference to the attached drawings, in which:

Figure 1 illustrates a sectional perspective view of a portion of a liquid ejection device provided with a nozzle plate including a nozzle, according to an embodiment of the present invention;

Figures 2-12 show, in sectional side view, manufacturing steps of the nozzle plate of Figure 1 according to an embodiment of the present invention;

Figures 13-19 show, in sectional side view, manufacturing steps of the nozzle plate of Figure 1 according to a further embodiment of the present invention;

figure 20 is a side sectional view of the liquid ejection device of figure 1, in which the nozzle plate including a plurality of nozzles is shown; And

Figure 21 illustrates a printing machine comprising the ejection device of Figure 1 or Figure 20.

Figure 1 shows, in perspective view, a liquid ejection element 1 according to an embodiment of the present invention. The liquid ejection element 1 comprises a plate (â € œplateâ €) 2 provided with one or more nozzles (â € œnozzlesâ €) 4 (only one nozzle 4 is shown in figure 1). In particular, the view of figure 1 shows the liquid ejection element 1 sectioned along a diameter of the nozzle 4 which, in this representation, has a substantially circular shape.

Below the plate 2 there is a tank 6 fluidically connected to the nozzle 4 by means of an ejection channel 8. The tank 6 is designed to contain a liquid to be ejected through the nozzle 4. The ejection is It is obtained, according to one embodiment, by means of a piezoelectric element (not shown in figure 1), having the function of an actuator to allow the ejection of the liquid through the nozzle 4. When activated by means of a suitable electronic command (not shown), this piezoelectric actuator induces a vibration that is transmitted to the liquid contained in the ejection channel 8, causing it to escape through the nozzle 4. Other types of actuators can be used, for example thermal actuators, operating according to â € œthermal inkjetâ € technology.

The nozzle 4 is made in the form of a hole which extends completely through the plate 2, in a region of the latter provided with a recess 2â € ™. The nozzle 4 forms a passage of the liquid contained in the tank 6 towards the outside of the liquid ejection element 1. An inlet section (â € œinlet sectionâ €) 4a of the nozzle 4 is directly fluidically coupled with the ejection channel 8, while an outlet section 4b of the nozzle 4 extends in correspondence with the recess 2â € ™. The distance, along the Z direction, between the inlet section 4a and the outlet 4b corresponds to the thickness of the plate 2. The outlet section 4b of the nozzle 4 has, in a top view (i.e. observing the nozzle 4 along direction Z) substantially circular shape with diameter d1. The inlet section 4a also has, in top view, a substantially circular shape, but with a diameter d2 greater than d1. This conformation of the nozzle 4, in which the inlet section 4a, directly coupled to the ejection channel 8, has a diameter d2 greater than the diameter d1 of the outlet section 4b, which extends in correspondence with the recess 2â € ™, has the advantage of allow the generation, during use, of ejected drops having a high output speed. In particular, the speed of these drops is greater than that which can be obtained by means of nozzles having a substantially cylindrical shape, in which the inlet section has a diameter approximately equal to the outlet section.

According to one embodiment, the recess 2â € ™ extends so as to at least partially surround the nozzle 4. According to a further embodiment, the recess 2â € ™ extends so as to completely surround the nozzle. 2â € ™ is delimited by walls 3 arranged at a distance from the nozzle 4, in such a way as not to hinder, and not interfere with, the ejection of the liquid during the use of the liquid ejection element 1 . For example, the walls 3 extend to a minimum distance DR, measured starting from the edge of the outlet section 4b of the nozzle 4, between about 3 µm and about 30 µm, in particular between about 5 µm and about 20 µm, for example equal to about 10 µm. The recess 2â € ™ extends into the structural layer 16 for a depth, measured starting from the upper surface of the structural layer 2, between 0.1 µm and 10 µm, for example equal to 1 µm.

The presence of the recess 2â € ™ allows to avoid that debris, for example deriving from the ejection process of the liquid from the nozzle 4, and / or unwanted material with which the plate 2 may come into contact during use, can interfere with the ejection of the liquid from the nozzle 4. In particular, if the plate 2 is placed in contact with a dirty surface, the outlet section 4b of the nozzle 4, being formed in the recess 2â € ™, is not be in direct contact with this dirty surface, thus reducing the possibility of clogging the nozzle 4.

According to an embodiment of the present invention, the nozzle plate 2 further comprises a protective layer 9 which extends in such a way as to cover the base surface of the recess 2 'and the walls of the hole which realizes the nozzle 4 (ie the walls that connect the inlet section 4a with the outlet section 4b). The protective layer 9 is made of a material that does not undergo significant degradation when placed in contact (even prolonged) with the liquid to be ejected through the nozzle 4. In this way, even in the case of ejections of corrosive liquids, the nozzle does not undergo such degradation as to compromise its effective use for the application in question. It is evident that the choice of the material used for the protective layer 9 depends on the type of use envisaged for the liquid ejection element 1. For example, if the liquid to be ejected is ink, materials that can be used for the protection 9 are, for example, silicon carbide, alumina, hafnium oxide, titanium, tantalum, tungsten and / or alloys thereof.

Figures 2-12 show manufacturing steps of the liquid ejection element 1 of Figure 1. In particular, manufacturing steps of the nozzle plate 2 and its coupling with channel 8 are described. The manufacturing steps of the tank 6 and its coupling with the ejection channel 8 are not the subject of the present invention and are therefore not described in detail below.

The view of the liquid ejection element 1 of figures 2-12 corresponds to the liquid ejection element 1 of figure 1 when observed parallel to the Y direction, orthogonal to the XZ plane.

With reference to Figure 2, according to an aspect of the present invention, a wafer 10 is arranged, comprising a substrate 11 of semiconductor material, for example silicon, having a substantially uniform thickness, included in the range from about 200 µm to about 800 µm, for example equal to about 400 µm. The substrate 11 has an upper face 11a and a lower face 11b, opposite each other along the direction of the Z axis.

Then, an intermediate layer 12 is formed on the substrate 11 to protect the substrate 11 during subsequent manufacturing steps. For example, the intermediate layer 12 is of silicon oxide (SiO2) and is formed, according to one aspect of the present invention, by thermal growth of SiO2 on the substrate 11 when the latter is of silicon. The intermediate layer 12 is, in particular, formed both on the upper face 11a and on the lower face 11b of the substrate 11.

According to a different embodiment of the present invention, the intermediate layer 12 is formed only at the upper face 11a of the substrate 11.

In any case, it is evident that the intermediate layer 12 can be formed by a technique other than thermal growth, for example by depositing material such as silicon oxide or silicon nitride (SiN), or still other material.

Regardless of the technique used to form the intermediate layer 12, the latter has a substantially uniform thickness, ranging from about 0.5 µm to about 2 µm, for example equal to about 1 µm.

Then, Figure 3, a sacrificial layer 14 is formed above the upper face 11a of the substrate 11, for example by means of a deposition technique. The sacrificial layer 14 can be either of a material that can be removed (â € œetchedâ €) together with the material of which the intermediate layer 12 is formed (i.e. by means of the same etching chemistry), or of a selectively attackable material with respect to the material of which the intermediate layer 12 is formed. For example, the sacrificial layer 14 is made of silicon oxide or silicon nitride, or some other material. The sacrificial layer 14 has a thickness comprised in the range from about 0.1 µm to about 10 µm, for example equal to about 1 µm.

In figure 4, the sacrificial layer 14 is selectively attached so as to remove the sacrificial layer 14 from the slice 10 except for regions where it is desired to form the recess 2â € ™ shown in figure 1. An island is thus formed sacrificial 14â € ™ which extends above the intermediate layer 12 and the upper face 11a of the substrate 11.

Then, figure 5, a structural layer 16 is grown on the wafer 10 (above the upper face 11a of the substrate 11, the intermediate layer 12, and the sacrificial island 14â € ™), for example by epitaxial growth of silicon. The structural layer 16 has a substantially uniform thickness, comprised in the range from about 5 µm to about 100 µm, and preferably from about 10 µm to 50 µm, for example equal to 20 µm. According to an embodiment of the present invention, the structural layer 16 is initially formed with a thickness greater than the desired thickness. We then proceed with a planarization phase, so as to reach a desired thickness (uniform on the wafer 10) and at the same time reduce the surface roughness of the structural layer 16. The planarization phase is carried out, for example, with the CMP technique ( â € œChemical Mechanical Planarizationâ €).

Then, figure 6a, the structural layer 16 is attached in such a way as to define an opening 18 in correspondence with the sacrificial island 14â € ™. The opening 18 contributes to forming, in subsequent manufacturing phases, the nozzle 4. As shown in figure 6b, the opening 18 has an extension, in top view, that is less than the extension of the sacrificial island 14â € ™ (ie the opening 18 is completely contained within the sacrificial island 14â € ™).

The attachment of the structural layer 16 to form the opening 18 is performed, for example, using the RIE technique (â € œReactive Ion Etchingâ €), and proceeds until the sacrificial island 14 is reached. , which operates, in this case, as an element of interruption of the attack (â € œetch stop elementâ €).

It is evident that, according to different embodiments of the present invention, the opening 18 can be formed by other etching techniques, wet or dry.

Regardless of the technique with which the opening 18 is formed, the latter has, according to the view of figure 6b, a substantially circular shape. In perspective view (not shown), the opening 18 has, according to one aspect of the present invention, a substantially cylindrical shape. The circular base of the opening 18 has a diameter chosen according to need, so that it is contained inside the sacrificial island 14â € ™. For example, the diameter is between 1 µm and 40 µm, more specifically between 5 µm and 25 µm. As better described below, due to subsequent manufacturing steps, the diameter of the opening 18 (measured during the step of figure 5) is greater than the diameter of the nozzle 4 at the end of the manufacturing steps.

Again with reference to figures 6a and 6b, a shrinking layer 20 is formed above the structural layer 16 and inside the opening 18. The shrinking layer 20 has a thickness between about 1 µm and about 5 µm, for example equal to 2 µm, and is of a material that can be selectively attacked with respect to the material of which the sacrificial island 14â € ™ is formed. For example, in the case in which the sacrificial island 14â € ™ is of silicon oxide, the shrink layer 20 is of silicon nitride. Conversely, in the case in which the sacrificial island 14â € ™ is of silicon nitride, the shrink layer 20 is of silicon oxide. However, other materials can be used.

The narrowing layer 20 extends, in particular, in correspondence with an internal wall 18â € ™ which laterally delimits the opening 18. Preferably, the thickness previously indicated for the narrowing layer 20 is measured at the internal wall 18â Opening 18.

Then, figure 7, the shrinking layer 20 is attached by direct (anisotropic) dry etching, shown in figure 7 by arrows 21. In this way, portions of the shrinking layer 20 extending orthogonally to the etching direction (i.e. portions of the of shrinkage 20 extending parallel to the XY plane) are removed faster than portions of the shrinking layer 20 extending parallel to the direction of attachment. Consequently, portions of the shrinking layer 20 extending above the structural layer 16 and above part of the sacrificial island 14 'are completely removed; instead, a portion of the narrowing layer 20 extending along the lateral wall (inner wall) 18â € ™ of the opening 18 is not completely removed, but is shaped (â € œshapedâ €) in such a way as to assume an at least partially tapered shape , that is, having a non-uniform DSPACER thickness (measured starting from the internal wall 18â € ™). In particular, the DSPACER thickness decreases moving away from the sacrificial island 14â € ™ along the Z direction. Thus a narrowing element 20â € ™ is formed extending into the opening 18 at and adjacent to the internal wall 18â € ™ of the opening 18 itself.

As can be seen from Figure 7, the step of etching of the shrinking layer 20 allows to model, during the same etching step, the shrinking element 20 'in the desired way, as previously described. The opening 18 thus assumes a shape which can be assimilated, according to one embodiment, to a truncated cone. In general, the narrowing element 20â € ™ is able to model the shape of the opening 18 in such a way that it presents a section (parallel to the XY plane and extending in correspondence with the sacrificial island 14â € ™) having a diameter smaller than the diameter of the section of the opening 18 (also considered parallel to the XY plane) extending in correspondence with the exposed surface of the structural layer 16. In general, the area of the section of the opening 18 extending in correspondence of the sacrificial island 14â € ™ is smaller than the area of the section extending in correspondence with the exposed surface of the structural layer 16. In use, at the end of the manufacturing phases, the section with the smallest area forms the outlet section ( â € œoutlet sectionâ €) of nozzle 4, while the larger area section forms the inlet section (â € œinlet sectionâ €) of nozzle 4.

Said restricting element 20â € ™ has the function of forming a nozzle 4 having a tapered shape, as already shown in figure 1 and described with reference to this figure. In particular, depending on the type of attachment used to remove the shrinking layer 20, and the duration of the attachment itself, the shrinking element 20â € ™ can take on a triangular shape (in section view) or a shape in sectional view) given by the union of a triangular portion and a quadrangular portion, in which the quadrangular portion extends as an extension of the triangular portion. In perspective view, this shape is similar to the superimposition of a truncated cone portion with a cylindrical portion. Obviously, since the shrinking element 20 'is monolithic and of the same material, the two portions extend one after the other with continuity, and without a clear separation. It is evident that this description of the shrinking element 20 'is qualitative. Irregularities with respect to the ideal geometric shape described, due to the manufacturing process, are possible.

Then, figure 8, the sacrificial island 14â € ™ is removed by wet attack. During this etching phase, the portion of the intermediate layer 12 which extends below the sacrificial island 14 ', until it reaches the substrate 11, is also removed. In this way a cavity 24 is formed which extends below of the shrinking member 20â € ™ and partially below the structural layer 16. In other words, the cavity 24 extends between the substrate 11 and the shrinking member 20â € ™, and between the substrate 11 and part of the structural layer 16.

In the event that the sacrificial island 14â € ™ and the intermediate layer 12 are made of materials that cannot be removed with the same etching chemistry, two successive attacks are necessary to remove the sacrificial island 14â € ™ and the portion of the intermediate layer 12 lying below the latter.

Then, figure 9, the protective layer 9 is formed, extending above the structural layer 16 and the narrowing element 20â € ™, and in correspondence with the walls delimiting the cavity 24. In particular, the protective layer 9 extends on the bottom of the cavity 24 (corresponding to the upper face 11a of the substrate 11 exposed during the steps of figure 8) and in correspondence with the portions of the structural layer 16 and the narrowing element 20â € ™ directly facing the cavity 24.

The protective layer 9 is, according to an embodiment of the present invention, deposited by means of an atomic layer deposition technique (â € œALDâ € “â € œatomic layer depositionâ €), depositing a material chosen from silicon carbide, alumina, oxide of hafnium, titanium, tantalum, tungsten and / or alloys thereof.

The protective layer 9 deposited with the ALD technique has a controlled thickness over the entire surface of the nozzle 4 (â € œconformal filmâ €). The ALD deposition technique makes it possible to form the protective layer 9 also inside the cavity 24, in correspondence with the surface 11a of the substrate 11, the structural layer 16, and the shrinking element 20â € ™.

The Applicant has verified that, with the ALD technique, good coverage of all the walls of the cavity 24 formed following the removal of the sacrificial island 14 'is obtained, even in correspondence with remote portions of the latter.

However, other CVD deposition techniques can be used. However, CVD techniques other than the ALD technique may not guarantee excellent coverage of the walls of cavity 24 in correspondence with remote portions of the latter.

Then, figure 10, a grinding step (â € œgrindingâ €) at the lower face 11b of the substrate 11 allows to completely remove the intermediate layer 12 which extends at the lower face 11b of the substrate 11, the substrate 11, and the portion of protective layer 9 formed on the upper face 11a of the substrate 11, so as to reach the structural layer 16.

In this way the plate 2 is formed comprising a nozzle 4 as described with reference to figure 1. The plate 2 has a first face 2a covered by the protective layer 9 and a second face 2b which has the recess 2â € ™ and the nozzle 4.

Figure 11a shows, in top view when observed from the second face 2b, the nozzle 4. As can be seen, the nozzle 4 has, in a top view and in correspondence with the recess 2â € ™, a substantially circular shape and has a diameter having a first value d1. The portion of the nozzle 4 in correspondence with the recess 2â € ™ is the section of the nozzle 4 from which, in use, the liquid is ejected.

It is evident that, according to further embodiments (not shown), the nozzle 4 can have, in top view and in correspondence with the recess 2 ', an elliptical, quadrangular, polygonal, or irregular shape, or other shape considered advantageous for the application foreseen for the nozzle 4.

Figure 11b shows, in top view when observed from the first face 2a, the nozzle 4. Also in correspondence with the first face 2a the nozzle 4 has a substantially circular shape, but in this case it has a diameter having a second greater value d2 of the first value d1. The portion of the nozzle 4 corresponding to the first face 2a is the section of the nozzle 4 directly facing the ejection channel 8, from which the liquid to be ejected is fed.

Therefore, returning to the sectional view of Figure 10, the nozzle 4 has a tapered region suitable to operate as a conjunction between the ejection channel 8 and the outlet section of the nozzle 4. The section of the tapered region having a larger diameter d2Ã configured to be directly facing the ejection channel 8, fluidically coupled to the latter.

The ejection channel 8 is formed starting from a substrate 30 of semiconductor material, for example silicon, processed by means of known microfabrication techniques (lithography and etching) in such a way as to form a channel 31 of a substantially cylindrical shape having a diameter dC of a base section greater than the diameter d2 (and consequently also the diameter d1) of the nozzle 4.

With reference to Figure 12, the substrate 30 is coupled to the first face 2a of the plate 2 by a known technique, for example slice-to-slice bonding (â € œwafer-towafer bondingâ €), or by means of glue, or by means of a double-sided adhesive layer, or in still another way. The coupling of the substrate 30 with the plate 2 is performed in such a way that the straight line, parallel to the Z axis, passing through the center of the nozzle 4, coincides with the straight line, parallel to the Z axis, passing through the center of the ejection channel 8.

According to an embodiment of the present invention, to facilitate the grinding operation described with reference to step 10, the step of coupling the substrate 30 to the plate 2 is performed before the grinding step of the substrate 11. In this way, during the grinding operation, the substrate 30 has the function of reinforcing the plate 2 and facilitating its handling.

Figures 13-19 show manufacturing steps of a liquid ejection element 100 according to a further embodiment of the present invention.

With reference to Figure 13, in a similar way to what has already been described with reference to Figure 2 for the respective embodiment, a wafer 100 is arranged, comprising a substrate 110 of semiconductor material, for example silicon, having a substantially uniform thickness, included in the range from about 200 µm to about 800 µm, for example equal to about 400 µm. The substrate 110 has an upper face 110a and a lower face 110b, opposite each other along the direction of the Z axis.

Then, an intermediate layer 112 is formed on the substrate 110 to protect the substrate 110 during subsequent manufacturing steps. For example, the intermediate layer 112 is of silicon oxide (SiO2) and is formed by thermal growth of SiO2 on the silicon substrate 110. The intermediate layer 112 is, in particular, formed both on the upper face 110a and on the lower face 110b of the substrate 110. It is evident that the intermediate layer 112 can be formed only in correspondence with the upper face 110a of the substrate 110.

In any case, it is evident that the intermediate layer 112 can be formed by a technique other than thermal growth, for example by deposition. Furthermore, the intermediate layer 112 can be of a material other than SiO2, for example of silicon nitride (SiN), or other material.

Regardless of the technique used to form the intermediate layer 112, the latter has a substantially uniform thickness, ranging from about 0.1 µm to about 10 µm, for example equal to about 1 µm.

Then, Figure 14, above the upper face 111a of the substrate 111 and the intermediate layer 120, a structural layer 116 is formed, for example by epitaxial growth of silicon. The structural layer 116 has a substantially uniform thickness, comprised in the range from about 5 µm to about 100 µm, and preferably from about 10 µm to 50 µm, for example equal to 20 µm. Then, the structural layer 116 is attached in such a way as to define an opening 118 which extends completely through the structural layer 116, until it reaches the intermediate layer 112.

The dislocation on the wafer 100, and the shape, of the opening 118 are similar to those already described with reference to Figures 6a and 6b of the respective embodiment. In this case, however, the sacrificial island 14â € ™ is not present.

Then, figure 15, above the structural layer 116 and inside the opening 118, a shrinkage layer (â € œspacerâ €) 120 is formed. The shrinkage layer 120 has a thickness between about 1 µm and about 5 µm, for example equal to 2 µm and is of a material that can be selectively attacked with respect to the material of which the intermediate layer 112 is formed. For example, in the case in which the intermediate layer 112 is of silicon oxide, the shrink layer 20 is silicon nitride. Conversely, in the case where the intermediate layer 112 is of silicon oxide silicon nitride, the shrink layer 20 is of silicon oxide. However, other materials can be used.

The narrowing layer 20 extends, in particular, in correspondence with the internal wall 18â € ™ which laterally delimits the opening 18. Preferably, the thickness previously indicated for the narrowing layer 20 is measured at the internal wall 18â € Of the opening 18.

Then, figure 16, the shrinking layer 20 is etched by direct (anisotropic) dry etching, shown by the arrows 121 in figure 16. In this way, portions of the shrinking layer 120 extending orthogonally to the etching direction (i.e. portions of the of shrinkage 120 extending parallel to the XY plane) are removed faster than portions of the shrinking layer 120 extending parallel to the direction of attachment. Consequently, portions of the shrink layer 120 extending above the structural layer 116 and above part of the intermediate layer 112 are completely removed; on the other hand, portions of the shrinking layer 120 extending along side walls 118 of the opening 118 are not appreciably affected. In this way a narrowing element 120â € ™ is formed extending into the opening 118 in correspondence with the lateral walls 118â € ™ of the same. As can be seen from Figure 16 (and as already described with reference to Figure 7), the etching step of the shrinking layer 120 models the shrinking element 120â € ™, in particular at their upper ends where the opening 118 assumes a substantially truncated cone shape.

Then, figure 17, an etching step is carried out to remove the portion of the intermediate layer 112 exposed through the opening 118. In particular, this etching step proceeds as long as a portion of the intermediate layer 112 also extends between the layer intermediate 112 and the structural layer 116 is removed. In this way, the shrinking element 120â € ™ and part of the structural layer 116 are partially suspended above the substrate 111.

The attack of the intermediate layer 112 according to the step of figure 17 is an isotropic attack (wet or dry attack).

According to a further embodiment, the shrinking element 120 'are of the same material of which the intermediate layer 112 is formed (for example of silicon oxide). In this case, the etching step according to figure 17 also removes part of the shrinkage element 120â € ™. However, by forming 120â € ™ spacers of appropriate thickness, it is possible to overcome this problem.

Then, Figure 18, a protective layer 109 is formed, extending over the structural layer 116 and the shrink member 120â € ™. In particular, the protective layer 109 also extends on the upper face 111a of the substrate 111 exposed during the step of figure 17, and in correspondence with the portions of the structural layer 116 and of the shrinking element 120â € ™ facing towards the upper face 111a substrate 111.

The protective layer 109 is similar to the protective layer 9 already described with reference to the previous figures 1 and 9, and is formed in the same way.

Then, figure 19, a step of grinding (â € œgrindingâ €) in correspondence with the lower face 111b of the substrate 111 allows to completely remove the intermediate layer 112 which extends in correspondence with the lower face 111b of the substrate 111, the substrate 111, and the portion of the protective layer 109 extending directly in contact with the upper face 111a of the substrate 111. By stopping the grinding step in this stage, a portion of the intermediate layer 112 remains surrounding the nozzle 104 such as to form a recess 112â € ™ in the intermediate layer 112. The 112â € ™ recess has, in use, the same function as the 2â € ™ recess in figure 1.

Alternatively, it is possible to stop the grinding at the end of the removal of the portion of the protective layer 109 extending directly on the upper face 11a of the substrate 11, and to remove the remaining intermediate layer 112 by means of a selective etching step, for example a wet etching. Then, a step of dry etching of the protective layer 109 is carried out in order to only partially remove the protective layer 109 around the nozzle 104, so as to form a recess similar to the recess 2 'of figure 1.

Regardless of the embodiment, a plate 102 is formed comprising a nozzle 104 which is similar to the plate 2 comprising the nozzle 4 described with reference to figure 1 and shown in this figure. The plate 102 has a first face 102a covered by the protective layer 109 and a second face 102b which has the recess 112 '.

Subsequently, the plate 102 is coupled with a substrate 130 similar to the substrate 30 described with reference to Figure 12, so as to fluidically couple the nozzle 104 to an ejection channel.

Figure 20 shows a liquid ejection device 200 comprising a plate 2 or 102 provided with a plurality of nozzles 4 or 104 and manufactured according to the method of Figures 2-12 or, respectively, according to the method of Figures 13-19.

The liquid ejection device 200 comprises a tank 6, arranged below the plate 2, 102 and able to contain in its own internal housing 202 a liquid substance 205 (for example ink) which, in use, must be made to escape from the nozzles 4; 104 through the ejection channels 6. The actuation of the liquid ejection device 200 can be carried out in various ways, for example by means of a piezoelectric type actuator 204, integral with a lower face of the tank 6 opposite the plate of the nozzles 2. Alternatively, they can be provided (in way not shown) a plurality of actuators, piezoelectric type or thermal ink-jet type, arranged in correspondence with a respective nozzle 4, 104, for example immediately below the respective nozzle 4, 104, in the ejection channel 8.

However, other ways of arranging the actuators are possible. For example, each nozzle 4, 104 can be fluidically coupled to a respective tank, and each tank can be provided with a respective actuation element 204. Or, again, a group of nozzles 4, 104 is fluidically coupled to the same tank , and another group of nozzles is fluidically coupled to a further tank. The tanks can be filled with different liquids.

With reference to figure 20, when activated by means of a suitable control electronics (not shown), the actuator 204 induces a vibration which is transmitted through the tank 6 to the liquid 205 contained in the housing 202, causing it to escape through the nozzles 4, 104.

According to an embodiment, an inlet 206 is provided for refilling the tank 6 with further liquid substance when this, following the use of the liquid ejection device 200, runs out. Alternatively, the liquid ejection device 200 is of the non-refillable type and the inlet port 206 is omitted.

According to an embodiment of the present invention, the liquid ejection device 200 is a print cartridge, for inkjet type printers.

Figure 21 schematically shows an ink jet printer 300 provided with a liquid ejection device 200 (acting as a print cartridge) which comprises a nozzle plate 2, 102 having a plurality of nozzles 4, 104 of the type described according to the present invention, and made according to the dictates of the present invention.

The ink jet printer 300 also comprises a control electronics 310, comprising a control card and / or a microprocessor and / or a memory for controlling and managing the printing operations.

The control electronics 310 can also comprise a frequency oscillator operatively coupled to the actuator 204, to control the oscillation frequency of the actuator 204, if the latter is of the piezoelectric type.

From an examination of the characteristics of the invention made according to the present invention, the advantages that it allows to be obtained are evident.

In particular, the invention according to the present invention is completely realized by means of a manufacturing process compatible with manufacturing technologies of the MEMS type, starting from a wafer of standard semiconductor material. Furthermore, the manufacturing process described requires a limited number of manufacturing steps, making it possible to produce low-cost, high-yield industrial specimens.

Furthermore, the shrinkage element 20â € ™, 120â € ™, formed as previously described, are self-aligned with the opening 18, 118 so that a further phase of alignment of the shrinkage element 20â € ™, 120â With the hole that defines the nozzle is not required.

Finally, it is clear that modifications and variations can be made to what is described and illustrated herein without departing from the protective scope of the present invention, as defined in the attached claims.

It is evident that the steps of the method described with reference to Figures 2-12 are applicable to the formation of a plurality of nozzles 4 housed in respective recesses 2â € ™ of the same nozzle plate 2.

According to a further embodiment, a recess 2â € ™ can house a plurality of nozzles 4.

Similarly, the steps of the method described with reference to Figures 2-12 are applicable to the formation of a plurality of nozzles 4 housed in respective recesses 2â € ™ of the same nozzle plate 2.

Claims (20)

CLAIMS 1. Process for manufacturing a nozzle plate (2) for a liquid ejection device (200), comprising the steps of: - arranging a first substrate (11; 111) of semiconductor material, having a first (11a; 111a) and a second (11b; 111b) face; - form a structural layer (16; 116) on the (â € œaboveâ €) first face (11a; 111a) of the first substrate, the structural layer having a first and a second face, the second face of the structural layer facing the first face of the first substrate; - remove a selective portion of the structural layer (16; 116) so as to form a first through hole (18; 118) having an internal wall (18â € ™), said first through hole having an inlet section (â € œinlet sectionâ €) at the first face of the structural layer and an outlet section (â € œoutlet sectionâ €) at the second face of the structural layer; - form a narrowing element (20; 20 '; 120') adjacent to the wall of the first through hole, - tapering the narrowing element in such a way that the inlet section of the first through hole has an area greater than a respective area of the outlet section of the first through hole; And - remove the first substrate so as to make the first through hole accessible. 2. Process according to claim 1, wherein the step of forming the shrinking element (20; 20 '; 120') comprises depositing, in the first through hole (18; 118), a shrinking layer (20 ) of a material which can be selectively attacked with respect to the material of the structural layer (16; 116), and in which the step of tapering the shrinking element (20 '; 120') comprises performing an anisotropic etching step of the shrinking layer (20) along a preferential etching direction substantially parallel to the wall (18 ' ) of the first through hole (18; 118). 3. Process according to claim 1 or 2, further comprising the step of forming a protective layer (9; 109) inside the first through hole and in such a way as to cover the narrowing element (20â € ™; 120â € ™) . 4. Process according to claim 3, in which the step of forming the protective layer (9; 109) comprises depositing, on the shrinking element (20â € ™; 120â € ™), a material selected from silicon carbide, alumina , hafnium oxide, titanium, tantalum, tungsten, and alloys thereof. 5. Process according to any one of the preceding claims, further comprising the step of forming an intermediate layer (12; 112) on the (â € œaboveâ €) first face (11a; 111a) of the first substrate, the step of forming the structural layer (16; 116) comprising forming said structural layer on the (â € œonâ €) intermediate layer (12; 112), the procedure also including: - attaching (â € œetchingâ €) the intermediate layer at the inlet section of said first through hole (18; 118); And - continue the attachment of the intermediate layer (12; 112) in order to remove a portion of the intermediate layer extending between the narrowing element (20 '; 120') and the first substrate (11; 111), and between a portion of the structural layer (16; 116) adjacent to the narrowing element (20â € ™; 120â € ™) and the first substrate (11; 111). 6. Process according to claim 5 when dependent on claim 3, wherein the step of forming the protective layer (9; 109) comprises forming the protective layer at portions of the shrinking element (20â € ™; 120â € ™ ) and of the structural layer (16; 116) facing the first substrate (11; 111). 7. Process according to any one of claims 1-4, further comprising the steps of: - form an intermediate layer (12; 112) on the (â € œaboveâ €) first face (11a; 111a) of the first substrate (11; 111); And - form a sacrificial island (14â € ™) on the (â € œonâ €) intermediate layer, the phase of forming the structural layer (16; 116) comprising forming said structural layer on the (â € œaboveâ €) intermediate layer and on the sacrificial island, and the step of forming the first through hole (18; 118) comprising forming said first through hole above the sacrificial island, and in such a way that the first through hole is completely contained by the sacrificial island, the process also including the step of selectively attacking the sacrificial island (14â € ™) and a portion of the intermediate layer (12; 112) extending below the sacrificial island (14â € ™) so as to form a cavity (24 ) extending partially between the first substrate (11; 111) and the structural layer (16; 116), and between the first substrate (11; 111) and the narrowing element (20â € ™; 120â € ™). 8. Process according to claim 7 when dependent on claim 3, wherein the step of forming the protective layer (9; 109) comprises forming the protective layer at surface portions of the shrinking element (20â € ™; 120â € ™) and of the structural layer (16; 116) facing said cavity (24). 9. Process according to any one of the preceding claims, further comprising the steps of: - arranging a second substrate (30) of semiconductor material; - attaching said second substrate (30) so as to form a second through hole (31) through said second substrate (30); - coupling the second substrate (30) to the structural layer (16; 116) so that the second through hole (31) is aligned with the first through hole (18; 118) along the same direction (Z) orthogonal to respective planes of storage of the second substrate (30) and of the structural layer (16; 116). 10. Nozzle plate (2) for a liquid ejection device (200), comprising: - a structural layer (16; 116) having a first and a second face; - at least a first through hole (18; 118), having an internal wall (18â € ™), extending through the structural layer, said first through hole having an inlet section (â € œinlet sectionâ €) in correspondence with the first face of the structural layer and an outlet section (â € œoutlet sectionâ €) corresponding to the second face of the structural layer; - a narrowing element (â € œnarrowing elementâ €) (20â € ™; 120â € ™) adjacent to the wall of the first through hole, and including a tapered portion such that the inlet section of the first through hole has an area greater than a respective area of the outlet section of the first through hole, said through hole and said narrowing element forming an ejection nozzle (4; 104) of said nozzle plate (2). 11. Nozzle plate according to claim 10, further comprising a recess (2â € ™) formed in the structural layer (16; 116), the first through hole (18; 118) being formed in the recess (2â € ™). 12. Nozzle plate according to claim 11, wherein the recess (2â € ™) extends into the structural layer for a depth of from about 0.1 µm to about 10 µm, forming a wall (3) around the ejection nozzle. 13. Nozzle plate according to claim 10, further comprising a cover layer (112) extending on the second face of the structural layer (116) and surrounding the ejection nozzle (104), so as to form a recess (112â € ™), delimited by a wall of the cover layer (112), around the ejection nozzle. 14. Nozzle plate according to any one of claims 11-13, wherein said wall extends to a minimum distance (DR) from the recess of between about 3µm and about 30µm, said distance being measured from one edge of the nozzle ejection (4). 15. Nozzle plate according to any one of claims 10-14, further comprising a protective layer (9; 109) covering the constricting element (20â € ™; 120â € ™), said protective layer being of a non-material damaged by said liquid. 16. Nozzle plate according to claim 15 when dependent on any of claims 11-14, wherein the protective layer (9; 109) extends into the recess (2â € ™; 112â € ™) so as to cover the layer structural (2). 17. Nozzle plate according to any one of claims 10-16, wherein the restricting element (20â € ™; 120â € ™) further comprises a substantially cylindrical portion extending in extension of said tapered portion between the tapered portion and the outlet section of the first through hole. 18. Nozzle plate according to any one of claims 10-17, further comprising a substrate (30) of semiconductor material provided with a second through hole (31), the substrate (30) being coupled to the structural layer (16; 116) in such a way that the second through hole (31) is aligned with the first through hole (18, 118) along the same direction (Z) orthogonal to respective planes of storage of the substrate (30) and of the structural layer (26; 116). 19. Liquid ejection device (200), comprising: - a tank (6) having an internal chamber (202) configured to contain a liquid substance (205); And an actuator (204) connected to the tank (6) and configured in such a way as to cause the expulsion of the liquid substance from the tank, characterized in that it further comprises a nozzle plate (2) according to any one of claims 10-18, fluidically coupled to the tank (6) to allow the expulsion of the liquid substance through the nozzle (4). Printing machine (300) comprising the liquid ejection device (200) according to claim 19.